Wiper and method of manufacturing the wiper

ABSTRACT

A sheet-like wiper of a nonwoven fabric formed by entangling fibers with each other by a high-pressure water jet stream, wherein an amount of micro-matter of 100 μm long or more falling-off therefrom is 20,000 pieces/m 2  or less, an amount of material dissolved therefrom into acetone is 340 mg/kg or less, and the water absorption is 8 ml/g or more.

TECHNICAL FIELD

The present invention relates to an industrial wiper suitably used in aclean room, in the electronic product industry or the pharmaceuticalproduct industry, requiring a high cleanness, and to a method formanufacturing the wiper.

BACKGROUND ART

A wiper using nonwoven material has widely been used in the domestic,medical and industrial fields as a disposable wiper because of its lowprice, while the functions thereof required for the respective fieldsare different from each other. For example, in the domestic use, a wiperrepresented by a dishcloth or a duster is required to have breakingstrength and bulkiness. In a domestic floor-sweeping wiper, thedust-absorption performance is important. In medical use, it is stronglyrequired that no heavy metals or fluorescent compounds, harmful to ahuman body, are contained therein because the wiper is used in place ofcotton gauze.

On the other hand, in industrial use, disposable wipers of nonwovenfabric have been used in various fields. Of them, in clean rooms of theelectronic product industry or the pharmaceutical product industry, thedisposable wipers of nonwoven fabric are used for manually wiping aceiling, a wall, a floor, a device or a jig for the purpose of keepingthe room very clean. Disposable wipers of nonwoven material are alsoused for wiping out dirt or unnecessary liquid adhered to a part beingproduced. While these wipers are usually provided in a dry state, theymay be provided in a state preliminarily moistened with liquid for thepurpose of facilitating the convenience of the user. Particularly, as aspecial-use wiper in a biological industry, the wiper may be subjectedto sterilization treatment such as EOG sterilization, hot steamsterilization, γ-ray sterilization or electronic beam sterilization toincrease the added value.

As the nonwoven fabric wiper used in a clean room in an industrial fieldmust has a high degree of cleanness, it is preferably of a single-sheetshape rather than a folded shape. That is, the disposable wiper isdisposed of when the surface thereof is contaminated. If the wiper is ofthe folded shape, it is disposed while an inner surface thereof is stillunused, which is uneconomical. At present, various sheet-like nonwovenfabric wipers have been marketed as commercial products, including indry and wet states, and they are used for operations not only in a cleanroom but also in many other field wherein there is a need for cleaningobjects.

Although the sheet-like nonwoven fabric wiper has been used in a cleanroom in an industrial field as described above, more excellent wiperssatisfying all of extremely high and various performances are stilldesired.

That is, a first important performance of the industrial-use wiper isthat it is free from the generation and falling-off of micro-dust. Whilethe dust has various sizes, micro-dust having a size of 100 μm long ormore, is fibrous matter (fiber dust) falling off from the wipermaterial. The adhesion of the fibrous matter (fiber dust) is a seriousproblem not only when the wiper is used in the clean room but also whena surface to be coated is cleaned prior to a coating operation.

Table 1 shows the performance of the conventional sheet-like nonwovenfabric wipers most popularly used in the market wherein A, B, C, D and Eare composed of wood pulp and polyester fiber, F and G are composed ofwood pulp and polyester fiber treated with resinous binder, and H iscomposed of rayon and polyester fiber. In all of the above-mentionedsheet-like nonwoven fabric wipers, a fibrous sheet web is subjected to ahigh-pressure water jet stream (a so-called water jet needling) toentangle fibers therein with each other to form a nonwoven fabric. I isa melt-blown nonwoven fabric wiper.

Chemical bond nonwoven fabrics or thermal bond nonwoven fabrics areunsuitable for the sheet-like nonwoven fabric wiper used in the cleanroom in view of impurities and the hand.

As is apparent from the measured values shown in Table 1 obtained by thepresent inventors, an amount of micro-matter (dust) of 100 μm long ormore falling off from the marketed sheet-like nonwoven fabric wiper issurprisingly as much as in a range from 22,500 pieces/m² which isminimum (H) to 100,000 pieces/m² or more (A to E used for generalpurposes). Accordingly, none of the conventional wipers has beensatisfactory in view of the amount of micro-matter falling-offtherefrom. Since the generation of such a large amount of micro-mattercauses various problems, it is necessary to reduce the same as much aspossible.

A second important required performance of the industrial-use wiper isthat an amount of material dissolved from the wiper into solvent is low.When the operator carries out the cleaning operation in the clean roomby the nonwoven fabric wiper, the wiper is often wetted with organicsolvent in the same way as the domestic duster is used while beingwetted with water. This is because the persistent contamination of resinor oil within a chamber, which is impossible to be wiped off with water,can be cleaned, for example, by acetone having a high dissolving power.However, this is problematic in that a large amount of material such asspinning oil, hydrophilic treatment agent, binder or oligomer in thepolyester fiber material (mainly composed of triethyleneglycol) isdissolved from the conventional nonwoven fabric wiper into the acetone.

If the wiper is coated with adhesive resin to restrict the falling-offof the above-mentioned fibrous micro-matter, the amount of materialdissolved into acetone further increases. Accordingly, it is necessaryto use alcohol (mainly isopropyl alcohol: IPA) as solvent for thecleaning operation, which is less problematic regarding dissolvedmaterial but weaker in dissolving power. Such a countermeasure reducesthe cleaning effect, and therefore a nonwoven fabric wiper low in theamount of material dissolved into acetone has been required. As isapparent from Table 1, A, B, F, G and I are unsatisfactory.

A third important performance required by the market is that the wiperhas large water absorption. Various aqueous solutions such as sulfuricacid or nitric acid are used in the clean room and often overflow ordrip. As the solution must be wiped up by the nonwoven fabric wiper insuch a case, the water absorption thereof is preferably large. As thesynthetic fiber inherently has small water absorption, the wiper usingthe synthetic fiber is coated with hydrophilic agent (surfactant) orsubjected to a hydrophilic treatment, which increases the amount ofmaterial dissolved from the wiper into acetone.

In the prior art, a cellulose component has been mixed in the nonwovenfabric material of the wiper to improve the water absorption. However,if pulp fiber is used as the cellulose component, the generation offibrous micro-matter increases. As apparent from Table 1, the waterabsorption of the conventional sheet-like nonwoven fabric wipers isgenerally in a range from 4 to 6 ml/g, and at most 8 ml/g or less.

As described hereinbefore, there has been no sheet-like nonwoven fabricwiper free from all the problems of the amount of fibrous micro-matterfalling-off therefrom, the amount of material dissolved therefrom intoacetone and the water absorption. At present, the consumer has used theconventional wipers with a risk the above-mentioned problems.Accordingly, the sheet-like nonwoven fabric wipers at a reasonableprice, capable of being largely consumed as disposable material arestill required.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a sheet-like nonwovenfabric wiper having a totally excellent performance being low infalling-off of micro-matter (dust) therefrom or in material dissolvedinto acetone therefrom, and large in water absorption, and a method formanufacturing the same.

The present inventors have diligently studied to solve theabove-mentioned problems and made the present invention.

The present invention is as follows:

1. A sheet-like wiper of a nonwoven fabric formed by entangling fiberswith each other by a high-pressure water jet stream, wherein an amountof micro-matter of 100 μm long or more falling-off therefrom is 20,000pieces/m² or less, an amount of material dissolved therefrom intoacetone is 340 mg/kg or less, and the water absorption is 8 ml/g ormore.

2. A wiper as defined by 1 mentioned above, wherein the amount ofmicro-matter of 100 μm long or more falling-off therefrom is 14,000pieces/m² or less, the amount of material dissolved therefrom intoacetone is 190 mg/kg or less, and the water absorption is 9 ml/g ormore.

3. A wiper as defined by 1 or 2 mentioned above, wherein the nonwovenfabric contains cellulose filament fiber of 40% by weight or more, andthe cellulose filament fiber is cupra-ammonium rayon.

4. A wiper as defined by 3 mentioned above, wherein the content of thecellulose filament fiber is 85% by weight or more.

5. A method for manufacturing a wiper, comprising a process forproducing nonwoven fabric of cellulose filament fiber by a wet typecellulose spun-bonding method wherein cupra-ammonium cellulose solutionis continuously coagulated, regenerated, rinsed, entangled, dried andtaken up to form a nonwoven fabric, a process for combining the nonwovenfabric with other nonwoven fabric if necessary, a process for cuttingthe nonwoven fabric to be a flat sheet-like wiper, a process for wettingthe wiper with liquid if necessary and/or a process for sterilizing thewiper if necessary, wherein the entanglement process is carried out byplacing a buffer plate having an opening degree in a range from 10 to47% on a non-entangled web and applying onto the buffer plate a waterjet stream having a total impact energy value (F) in a range from0.5×10⁹ to 3.0×10⁹ joule·newton/kg to entangle fibers in the web.

The present invention will be described in more detail below.

The wiper referred to in this text is a wiper obtained by cutting anonwoven fabric which is a raw material into a sheet and supplied as aflat sheet-like product. A shape of the sheet may be any of square,rectangular, circular or polygonal or others.

Since the inventive wiper is used while being flatly gripped by a handof the operator, the breaking strength and the flat shape-retainingproperty durable against the use are required.

The inventive wiper is composed of a nonwoven fabric in which fibers areentangled with each other by the action of the high-pressure water jetstream. As this nonwoven fabric has the breaking strength sufficient formaintaining the shape thereof even if it is gripped by the operator'shand and additives such as a binder are unnecessary, it has an advantagein that the amount of material dissolved into acetone is reduced.Further, even if a relatively large amount of cellulose filament fiberis used, fibers are entangled with each other by the high-pressure waterjet stream to be an integral body, a high water absorption isobtainable.

While the inventive wiper is composed of a nonwoven fabric obtained byentangling fibers therein with each other by the high-pressure water jetstream, other fiber-entangling means may be used together with theformer for obtaining the nonwoven fabric, unless the effect of thepresent invention is deteriorated.

The present inventors have found that a nonwoven fabric obtained byentangling fibers with each other solely by means other than thehigh-pressure water jet stream is problematic. For example, in a casewherein fibers are press-bonded by a high-pressure embossing treatment,the fibers are easily separated from each other by friction orre-wetting. When fibers are bonded together by a resinous binder, thereis a problem in that the resin is dissolved in acetone. When fibers arebonded together by melting heat-fusible fibers preliminarily mixed withthem, a large amount of the heat-fusible fiber must be mixed for thepurpose of reducing an amount of micro-matter falling-off from thewiper, which causes a hard hand feeling and is unsuitable for a wiper.

The inventive wiper is not obtainable from a nonwoven fabric resultedfrom a melt blown method. This is because material used in the meltblown method is limited to heat-fusible synthetic fiber polymer whichgenerates a large amount of material dissolved in acetone, whereby suchmaterial is unsuitable for the inventive wiper.

The inventive wiper includes those used in a dry state and a wet stateif necessary. Also, the inventive wiper may include those subjected to asterilization treatment.

According to the inventive wiper, an amount of micro-matter of 100 μmlong or more falling-off therefrom is 20,000 pieces/m² or less,preferably 14,000 pieces/m² or less. The amount of micro-matter ispreferably as little as possible, most preferably zero. If the amount ofmicro-matter of 100 μm long or more falling-off therefrom is 20,000pieces/m² or less, the satisfactory performance is obtainable, ofcourse, in a clean room and also in the cleaning operation of a surfaceto be coated prior to the coating operation.

According to the inventive wiper, an amount of material dissolved inacetone is 340 mg/kg or less, preferably 190 mg/kg or less. The amountof material dissolved in acetone is preferably as little as possible,most preferably zero. If the amount of material dissolved in acetone is340 mg/kg or less, acetone having a high dissolving power is usable, andtherefore, the persistent contamination of resin or oil within achamber, which is impossible to be wiped off with water or alcohol, canbe cleaned.

The inventive wiper has the water absorption of 8 ml/g or more,preferably 9 ml or more. If the water absorption is 8 ml/g or more,various aqueous solutions such as sulfuric acid or nitric acid can besufficiently wiped off. While an upper limit of the water absorption isnot clearly determined, if it exceeds 20 ml/g, the wiper becomes anaqueous gel which is difficult to maintain its shape as a wiper.Accordingly, the water absorption does not exceed 20 ml/g.

The inventive wiper contains cellulose filament fiber of 40% by weightor more, preferably 85% by weight or more. Further, the cellulosefilament fiber is preferably cupra-ammonium rayon fiber. If thecellulose filament fiber is 40% by weight or more, the water absorptionbecomes 8 ml/g or more, and if the cellulose filament fiber is 85% byweight or more, the water absorption becomes 9 ml/g or more. The contentof the cellulose filament fiber is preferably as much as possible, mostpreferably 100% by weight.

For manufacturing the inventive wiper, a method is proposed, wherein anonwoven fabric formed by entangling cellulose filament fibers with eachother, by a water jet stream under specific conditions, is cut into aplurality of flat sheets.

The high-pressure water jet stream technology used for manufacturing aspun-lace nonwoven fabric is known as a hydro-entangling method. Also,in the method for manufacturing a wet type cellulose spun bondednonwoven fabric using a cupra-ammonium cellulose stock solution, thehigh-pressure water jet stream is used as an entangling method.

A total impact energy value (F) of the water jet stream applied to thenonwoven fabric web is represented by a product of an impact power (I)and a water jet energy (E): i.e., I×E which SI unit is J·N/kg. In thisregard, I=2 PA′ wherein P is a pressure of a water jet stream [pascal]and A′ is 0.6 A wherein A is a total cross-sectional area of a nozzle[m²]. Also E=PQ/wzv wherein Q is a total amount of water jet stream[m³/sec], w is a fabric weight [kg/m²], z is a width of the nonwovenfabric web [m] and v is a running speed of the nonwoven fabric web[m/sec].

In the inventive method, the total impact energy value (F) is in a rangefrom 0.5×10⁹ to 3.0×10⁹ [joule·newton/kg].

In the usual high-pressure water jet technology, the F value must be100×10⁹ or more, and in some cases, the entangling treatment is carriedout at a high F value of 1800×10⁹ or more. However, it has been foundthat the wiper obtained from such an excessively entangled nonwovenfabric is liable to generate a large amount of fibrous micro-matterfalling-off therefrom. That is, the present inventors have found that ifthe nonwoven fabric web is obtained under the usual entanglingcondition, the fibers are complicatedly bent and entangled with eachother within the interior of the web to form a number of loops which arebroken during the cutting process for manufacturing the wiper and form asource of fibrous micro-matter. Based on such a knowledge, the presentinvention has been made.

As described above, as the flat sheet-like nonwoven wiper is used bybeing gripped by the operator's hand while maintaining a sheet shape, adry breaking strength is preferably 1.5 kgf/5 cm width or more. If thetotal impact energy value is excessively low in the entanglingtreatment, the breaking strength of the sheet-like nonwoven wiper isinsufficient. Therefore, such a nonwoven fabric must be used as a wiperof a folded shape.

In view of the above-mentioned problem, the inventive method is anepoch-making technique for achieving the dry breaking strength necessaryfor the sheet-like nonwoven fabric wiper solely by imparting less totalimpact energy than that thought of in the prior art as well asdecreasing the number of micro-loops in the nonwoven fabric.

According to the inventive method, when the entangling treatment iscarried out, a buffer plate having an opening degree in a range from 10to 47% is placed on the nonwoven fabric web supported by a net, and thewater jet stream is applied to the nonwoven fabric web from above thebuffer plate. That is, by providing the buffer plate, the continuousapplication of the impact energy to all over the nonwoven fabric web isavoided, and instead, the energy is intermittently applied to necessaryportions of the nonwoven fabric web in a spotted manner, whereby it ispossible to decrease the number of fiber loops as much as possible andalso reduce the amount of fibrous micro-matter falling-off from the webto a large extent, as well as to achieve a sufficient dry breakingstrength as the sheet-like nonwoven fabric wiper. Also, as fibers in theweb are prevented from entering meshes of the net supporting thenonwoven fabric web by using the buffer plate, there is no breakage offibers which has often occurred when the nonwoven fabric web is strippedoff from the net in the conventional method whereby the generation offibrous micro-matter is furthermore restricted.

In the present invention, if the opening degree of the buffer plate isless than 10%, a large amount of water jet stream is splashed above thebuffer plate to disturb the stable operation, whereby fibers in thenonwoven fabric web are not sufficiently entangled with each other toresult in the nonwoven fabric instable in shape. On the other hand, ifthe opening degree of the buffer plate exceeds 47%, the buffering effectbecomes less to form the fibrous loops all over the web surface. Theopening degree of the buffer plate is more preferably in a range from 20to 40%.

A position of the buffer plate may be fixed, or may be adjustable, forexample, in the running direction of the nonwoven fabric web or oppositethereto. Also, the buffer plate is located between the water jet nozzleand the nonwoven fabric web. In this regard, a distance between thenonwoven fabric web and the buffer plate is preferably in a range from 5to 25 mm. A typical buffer plate is a metallic or plastic plain weavenet. Alternatively, a perforated plate in which through-holes and shieldportions are mixed may be used. The size of the through-hole ispreferably 3 mm² or less.

As described above, according to the present invention, an excellenteffect is obtainable by skillfully combining the total impact energyvalue (F) of the water jet stream in the entangling treatment with thebuffer plate. The nonwoven fabric treated with the water jet stream iscut as it is or after being combined with other nonwoven fabric intosheet-like pieces to be the inventive sheet-like nonwoven fabric wiper.

According to the present invention, to obtain the sheet-like nonwovenfabric wiper having the water absorption of 8 ml/g or more, the nonwovenfabric preferably contains water-absorbable fibers such as rayon,cotton, jute, pulp, polyvinyl alcohol or polyacrylonitrile fibers.

A nonwoven fabric containing solely non-water absorbable fibers (such aspolyester, polyamide or polypropylene fibers) has the water absorptionof 3 ml/g or less. While there is a nonwoven fabric wiper imparted withhydrophilic oil for the purpose of improving the water absorption, thewater absorption thereof is at most 4.9 ml/g, and on the other hand, theamount of material dissolved into acetone reaches 10,000 mg/kg. Even ina wiper containing polyester fibers of 100% subjected to the hydrophilictreatment, the amount of material dissolved into acetone reaches 1,545mg/kg. Accordingly, to obtain a high water absorption without increasingthe amount of material dissolved into acetone, the cellulose fibers suchas rayon fibers (viscose rayon or cupra-ammonium rayon) are preferablymixed.

According to the present invention, as the total impact energy of thewater jet stream is small in the entangling treatment, the resultant webis rich in bulkiness in comparison with the conventional product. Forexample, if the content of the rayon fiber is 40% by weight or more, thewater absorption of the resultant wiper is 8 ml/g, and if the content ofthe rayon fiber is 85% by weight or more, the water absorption of theresultant wiper is 9 ml/g or more. On the other hand, according to theconventional method, when the entangling treatment is carried out byusing the water jet stream having a total impact energy value (F) of1180×10⁹, the water absorption is 6.4 ml/g which is not so high as inthe present invention even if the content of rayon fiber is 60% byweight.

The cellulose fiber used is preferably rayon filament fiber such ascupra-ammonium rayon filament fiber for the purpose of reducing theamount of fibrous micro-matter falling-off therefrom. While the waterabsorption can be facilitated by using cotton fiber as a waterabsorbable component, a nonwoven fabric of 100% cotton is problematicbecause oil remaining in natural cotton fibers is dissolved intoacetone. The amount of material dissolved into acetone of the marketednonwoven fabric wiper of 100% cotton is approximately 1,700 mg/kg.Accordingly, it is necessary to restrict the content of cotton, if used,to not increase the amount of material dissolved into acetone. Althoughpulp fibers may be used as a component of the water absorbable fibers,the fiber length thereof is too short to sufficiently entangle thefibers with each other, whereby the amount of fibrous micro-matterfalling-off from the wiper is liable to increase.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail below withreference to the preferred embodiments. Note the present inventionshould not be limited by these embodiments.

The measurements are as follows:

(1) Amount of Micro-Matter Falling-Off from Wiper

A sample of a wiper was put into clean water of 300 ml in a 1 literbeaker and subjected to the radiation by a supersonic wave for 15minutes to move dust from the sample into water. After taking out thesample, the water was suckingly filtrated through a black celluloseester membrane filter of 4.7 cm diameter (manufactured by ADVANTEX Co.;a bore size of 0.8 μm; having a grating), and the number of micro-matterof 100 μm long or more caught on the surface of the filter was countedafter image-processing by a color imaging computer (software used; animage processing and analysis software Image Hyper-L provided fromINTERQUEST Co.; a binary processing threshold value 110), while beingconverted to the number of pieces per 1 m² of the sample.

(2) Amount of Material Dissolved into Acetone

A sample of 40 g weight was immersed into acetone of 640 ml at 20° C.for 15 hours to dissolve material in the sample into the acetone toobtain a solution. The solution containing the material was suckinglyfiltrated through a membrane filter of 1 μm cut (manufactured byADVANTEX Co. of 47 mm diameter; a PTFE plain surface filter) to removesolid residue, and a volume A (ml) of the filtrated solution wasmeasured.

The solution was condensed in an evaporator to 100 ml or less and,thereafter, vaporized and dried. An amount B (g) of non-volatile residuewas measured, from which the amount of material dissolved into acetonewas calculated by the following formula:Amount of material dissolved into acetone (mg/kg)=(B/A)×16×10⁶

(3) Water Absorption

A sample was left in a room conditioned at 20° C. and 65% RH for 15hours, and then cut into a size of 10 cm square which weight W₁ (g) wasmeasured. The sample was placed on a 10 mesh metallic net formed of awire of 0.5 mm diameter and immersed in water at 20° C. for 30 secondstogether with the net. Thereafter, the sample was horizontallymaintained in air on the metallic net for 10 minutes to remove water,and the weight thereof (W₂) was measured again. The water absorption wascalculated by the following formula.Water absorption (ml/g)=(W ₂ −W ₁)/W ₁

EXAMPLES 1 AND 2 AND COMPARATIVE EXAMPLES 1 AND 2

A cellulose filament fiber nonwoven fabric obtained by continuouslysolidifying and regenerating cupra-ammonium cellulose solution by a wettype method was subjected to the entangling treatment by a water jetstream while variously changing the total impact energy value (F).

The entangling treatment was carried out by placing the nonwoven fabricweb on a 40-mesh plain weave net, covering the nonwoven fabric web witha buffer plate formed of a 18-mesh plain weave net having an openingdegree of 25%, while fixing the buffer plate at a height of 10 mm abovethe nonwoven fabric web, and ejecting the water jet stream to thenonwoven fabric web through the buffer plate. The nonwoven fabric web isdried and cut into a square shape of 22.8 cm×22.8 cm to result in asheet-like nonwoven fabric wiper.

Results are shown in Table 2, from which are seen the following:

In J which is Comparative example 1, fibers were hardly entangled toeach other and the dry breaking strength was as weak as 0.3 kgf/5 cmwidth, which is unsuitable for the wiper.

K and L which are Examples 1 and 2, respectively, had excellentperformance suitable for the wiper.

M which is Comparative example 2 was unsatisfactory in the amount ofmicro-matter falling-off therefrom.

EXAMPLES 3 TO 5 AND COMPARATIVE EXAMPLE 3

As shown in Table 3, two sheets of a cellulose filament fiber nonwovenfabric obtained by continuously solidifying and regeneratingcupra-ammonium cellulose solution by a wet type method were prepared,and a predetermined amount of rayon staple fibers or polyester staplefibers was sandwiched between the two sheets by a method disclosed inJapanese Patent Publication No. 2578503 to result in a compositenonwoven fabric web.

This composite nonwoven fabric web was subjected to the entanglingtreatment by a water jet stream while variously changing the totalimpact energy value (F). The entangling treatment was carried out byplacing the nonwoven fabric web on a 70-mesh plain weave net, coveringthe nonwoven fabric web with a buffer plate formed of a 18-mesh plainweave net having an opening degree of 25%, while maintaining the bufferplate at a height of 20 mm above the nonwoven fabric web and moving thebuffer plate in the same direction as the moving direction of thenonwoven fabric web at a speed of 1/10 of the web running speed, andejecting the water jet stream to the nonwoven fabric web through thebuffer plate. The nonwoven fabric web is dried and cut into a squareshape of 22.8 cm×22.8 cm to result in a sheet-like nonwoven fabricwiper.

Results are shown in Table 3, from which are seen the following:

N which is Comparative example 3 was unsatisfactory in the amount ofmicro-matter falling-off therefrom and in the water absorption.

P, Q and R which are Examples 3, 4 and 5, respectively, had excellentperformance suitable for the wiper.

EXAMPLES 6 AND 7 AND COMPARATIVE EXAMPLES 4 AND 5

A cellulose filament fiber nonwoven fabric obtained by continuouslysolidifying and regenerating cupra-ammonium cellulose solution by a wettype method was subjected to the entangling treatment by using variousbuffer plates shown in Table 4 with a water jet stream having the totalimpact energy value (F) of 2.7×10⁹ (joule·newton/kg). In this regard,the buffer plate was fixed at a height of 20 mm above the nonwovenfabric web. The nonwoven fabric web was dried and cut into a squareshape of 22.8 cm×22.8 cm to result in a sheet-like nonwoven wiper.

Results are shown in Table 4, from which are seen the following:

In S which is Comparative example 4, fibers were hardly entangled witheach other to have a weak strength and difficult to maintain its fabricshape, whereby it was unsuitable for a wiper.

T and U which are Example 6 and 7, respectively, had excellentperformance suitable for the wiper.

V which is Comparative example 5 is unsatisfactory in the amount ofmicro-matter falling-off therefrom. TABLE 1 Amount of Amount ofmicro-matter material longer than extracted into Water 100 μm acetoneabsorption Brand Composition (pieces/m²) (mg/kg) (ml/g) A TEXWIPE Co.Pulp 55% 142,000 395 5.3 Technicloth Polyester 45% B Lymtech Co. Pulp55% 122,800 355 5.4 C1 Polyester 45% C Berkshire Co. Pulp 55% 105,700243 5.4 DURX 670 Polyester 45% D Dupont Co. Pulp 55% 140,000 133 4.6Micropure AP Polyester 45% E Dupont Co. Pulp 44% 125,500 206 5.6Micropure 100 Polyester 56% F TEXWIPE Co. Pulp 55%  47,200 2073 4.6Technicloth III Polyester 45% G Berkshire Co. Pulp 55%  29,100 2930 5.3DURX 770 Polyester 45% H Dupont Co. Rayon 40%  22,500 217 7.7 Micropure10 Polyester 60% I Kimbery Co. Polypropylene great many 9880 4.9 Crew100% (impossible to measure)

TABLE 2 Strength at break in Amount of Amount of dry state Total micro-material (in the impact matter extracted lateral Fabric energy longerthan into Water direction) weight value (F) 100 μm acetone absorption(kgf/5 cm Composition (kg/m²) (J · N/kg) (pieces/m²) (mg/kg) (ml/g)width) J Comparative Cellulosic 0.05  0.41 × 10⁹ — — — 0.3 example 1filament fiber 100% K Example 1 Cellulosic 0.05 0.503 × 10⁹ 1,227 132 151.5 filament fiber 100% L Example 2 Cellulosic 0.05  2.95 × 10⁹ 9,262 8711.1 2.2 filament fiber 100% M Comparative Cellulosic 0.05 87.86 × 10⁹24,300 121 10.5 2.9 example 2 filament fiber 100%

TABLE 3 Amount of Amount of material micro-matter extracted Fabric Totalimpact longer than into Water weight energy value 100 μm acetoneabsorption Composition (kg/m²) (F) (J · N/kg) (pieces/m²) (mg/kg) (ml/g)N Comparative Cellulosic 0.075 7.0 × 10⁹ 53,400 120 7.5 example 3filament fiber 73% Rayon staple fiber 27% P Example 3 Cellulosic 0.0752.8 × 10⁹ 18,390 117 11.5 filament fiber 73% Rayon staple fiber 27% QExample 4 Cellulosic 0.075 2.7 × 10⁹ 14,130 205 8.3 filament fiber 73%Polyester staple fiber 27% R Example 5 Cellulosic 0.075 0.60 × 10⁹ 6,200 315 8 filament fiber 40% Polyester staple fiber 60%

TABLE 4 Total Amount of Amount of impact micro- material energy matterextracted Fabric value Opening longer than into Water weight (F) Bufferdegree 100 μm acetone absorption Composition (kg/m²) (J · N/kg) plate(%) (pieces/m²) (mg/kg) (ml/g) S Comparative Cellulosic 0.05 2.7 × 10⁹30 8 — — — example 4 filament mesh fiber 100% double twill weave TExample 6 Cellulosic 0.05 2.7 × 10⁹ 25 32 5,590 105 12.5 filament meshfiber 100% plain weave U Example 7 Cellulosic 0.05 2.7 × 10⁹ 8 mesh 46.28,600 120 11 filament plain fiber 100% weave V Comparative Cellulosic0.05 2.7 × 10⁹ none 100 26,900 92 9.5 example 5 filament fiber 100%

CAPABILITY OF EXPLOITATION IN INDUSTRY

As the inventive sheet-like nonwoven fabric wiper is low in the amountof micro-matter falling-off therefrom and material dissolved intoacetone as well as more in water absorption, it is extremely suitablefor an industrial wiper used in a clean room or for a surface cleaningprior to the coating operation. Also, as acetone having a highdissolving power can be used, it is possible to completely cleanpersistent contamination of resin or oil in a chamber as well as tosufficiently wipe up various aqueous solutions such as sulfuric acid ornitric acid.

1. A sheet-like wiper of a nonwoven fabric formed by entangling fiberswith each other by a high-pressure water jet stream, wherein an amountof micro-matter of 100 μm long or more falling-off therefrom is 20,000pieces/m² or less, an amount of material dissolved therefrom intoacetone is 340 mg/kg or less, and the water absorption is 8 ml/g ormore.
 2. A wiper as defined by claim 1, wherein the amount ofmicro-matter of 100 μm long or more falling-off therefrom is 14,000pieces/m² or less, the amount of material dissolved therefrom intoacetone is 190 mg/kg or less, and the water absorption is 9 ml/g ormore.
 3. A wiper as defined by claim 1 or 2, wherein the nonwoven fabriccontains cellulose filament fiber of 40% by weight or more, and thecellulose filament fiber is cupra ammonium rayon.
 4. A wiper as definedby claim 3, wherein the content of the cellulose filament fiber is 85%by weight or more.
 5. A method for manufacturing a wiper, comprising aprocess for producing nonwoven fabric of cellulose filament fiber by awet type cellulose spun-bonding method wherein cupra-ammonium cellulosesolution is continuously coagulated, regenerated, rinsed, entangled,dried and taken up to form a nonwoven fabric, a process for combiningthe nonwoven fabric with other nonwoven fabric if necessary, a processfor cutting the nonwoven fabric to be a flat sheet-like wiper, a processfor wetting the wiper with liquid if necessary and/or a process forsterilizing the wiper if necessary, wherein the entanglement process iscarried out by placing a buffer plate having an opening degree in arange from 10 to 47% on a non-entangled web and applying onto the bufferplate a water jet stream having a total impact energy value (F) in arange from 0.5×10⁹ to 3.0×10⁹ joule·newton/kg to entangle fibers in theweb.